1. Field of the Invention
The present invention relates to a throttle lever device for a small-sized vehicle. Particularly, the invention is directed to a throttle lever device wherein the length of throttle cable pulled is changed in accordance with the amount of operation of an operating lever, thereby making the opening of a throttle valve in a carburetor variable.
2. Description of the Background Art
A conventional throttle lever device is disclosed in Japanese Patent Publication No. 1193/91. According to the background art disclosed therein, the amount of rotation of an operating lever and the length of a cable pulled thereby remain proportional to one another. This results in a flat operation feeling from a low speed range up to a full open range by operation of the operating lever.
According to the above conventional structure, the amount of operation of the operating lever is restricted to some extent, so when a carburetor throttle valve of a large diameter is to be operated, it is difficult to obtain a balance between the stroke and the load. on the other hand, in Japanese Utility Model Laid Open No. 37493/88, a throttle lever device is disclosed wherein the length of cable to be pulled is changed in accordance with the amount of operation of an operating lever. According to the construction disclosed therein, parallel links are used to change the length of the cable to be pulled relative to the amount of operation of the operating lever.
In the above construction, the device is large because parallel links are used. Particularly, a large external form results in an increase in size of the entire device, making it difficult to attach the device to the grip portion. Further, the links swing a large amount with respect to each other, and hence it is not convenient to use the device. Still further, the number of parts used increases and it is not easy to assemble the throttle operating mechanism. Since the amount of swing motion of the operating portion is large, especially that of the link mechanism, the device is difficult to position within a cover. If an attempt is made to accommodate the device within the cover, an extremely large sized cover must be used, which is not desirable. If the link mechanism is used on a snowmobile and exposed in an uncovered state, it is necessary to implement separate measures against the entry of snow into the mechanism.